1. Field of the Invention
This invention relates to couplings for tubes and is concerned more particularly with a tube coupling of the kind having a body member containing a collet for gripping the tube.
2. Prior Art
The body member may be a device to which the tube is to be coupled or it may contain two collets for holding the ends of separate tubes which are to be connected together. It is known to have a collet with resilient arms, the arms being forced inwardly by axial movement of the collet, the arms for this purpose having an outer tapered surface co-operating with a cam surface on said body member surrounding the collet. This cam surface may be an internal surface on the body member tapering in one axial direction and engaging the arms of the collet, the surfaces being such that the arms are forced inwardly by axial movement of the collet in the direction of withdrawal of the tube from the coupling. If a tube is pushed into the coupling through the collet from the end thereof remote from the arms so as to be gripped by the collet, any pull on the tube tends to pull the collet out and, by engagement with the tapering surface on the surrounding member, the arms of the collet are forced inwardly to grip the tube more firmly. The tube can be released however by holding the collet axially inwardly of said member so ensuring that the arms are not moved radially inwardly; the tube can then be withdrawn by overcoming any frictional or resilient grip between the arms and the tube.
As is described in my earlier U.S. Pat. No. 4,005,883, such a tube coupling can be constructed with a body member having an internal surface which tapers to a narrower diameter towards one end of the body member and the collet can be inserted through this narrow diameter portion of the body member by arranging the arms such that they can, in the absence of any tube within the collet, be forced sufficiently far inwardly to permit the arms passing through this narrow diameter portion.